The objective of this research is to characterize blood flow in normal and infarcted heart muscle quantitatively with improved spatial and temporal resolution through the use of stereologic techniques and computer-based analysis of images produced by diffusible and non-diffusible flow markers. First, the effect of radionuclide microsphere concentration and isotope energy on the resolution of flow as provided by autoradiographs will be determined. Then, differences and similarities of flow gradients demonstrated by radionuclide labelled microspheres, 14C-antipyrene, and Thioflavin-S will be identified and analyzed. Next, flow gradients in tissue will be correlated with histomorphologic features of those tissues in and adjacent to infarcts at various time intervals following coronary artery ligation. Finally, a double-isotope radioautographic method and gamma camera imaging technique will be developed to allow quantitative regimal analysis of flow at two different times in the same animal. Serial slices of hearts will be used to produce autoradiographs and fluorescence images. Representative tissue sections will be prepared from these slices using stains for lipids and dehydrogenase enzymes. Flow marker concentration will also be determined by radioactivity counts found from small pieces of tissue. A computer-based system will be employed to carry out detailed analyses of the flow marker images produced during this study. Data will be derived in the form of topographic maps, average flow marker content in bands of tissue, and histograms of flow marker distribution in arbitrarily shaped operator-determined regions. It is anticipated that this research will extend our understanding of blood flow in normal heart muscle as well as in cases of ischemia.